This invention relates to ultrasonic diagnostic imaging system probes that require the use of a coupling material, in particular to a guide for controlling the size and shape of the coupling material.
Ultrasonic diagnostic imaging systems are in widespread use for performing ultrasonic imaging and measurements of the human body through the use of probes which may be placed internal or external to the body being measured. The probes are used to view the internal structure of a body by creating a scan plane. The scan plane is produced from an array of transducers that transmit pulses or beams of energy into the body and receive returning echoes of energy as they are reflected from internal structures of the body. The scan plane is essentially the field of view inside the body being measured.
Probes that are inserted into the body for scanning, such as transrectal and transvaginal probes, often require the use of a coupling material between the transducer and the surface being examined. Such probes may have multiple transducers mounted in different positions at the distal end of the probe to obtain multiple scan planes. The transducer may also be rotatable in the distal end of the probe to provide multiple scanning planes.
Coupling materials emulate body tissue and are important in scanning a surface that is in close contact with the surface of the transducer. In such cases, the coupling material acts as a standoff, which allows the transducer to focus on the surface being examined. The coupling material must be placed between the transducer and the surface being examined to create a constant gap or distance that emulates body tissue. If a constant distance is not maintained between the transducer and the surface being examined, then the image quality of the scanned region may become diminished as the probe is unable to focus on tissues close to the transducer.
In procedures such as prostate brachytherapies or biopsies, the prostate gland is scanned with a probe that is inserted into the rectum of the patient being examined. The user of the probe may insert a needle into the prostate to deposit radioactive seeds or to take samples of cellular material. The probe is used to obtain an image of the prostate and an image of the needle while it is inserted in the prostate. The probe can also be used to stabilize or hold the prostate still by applying pressure to the interior wall of the rectum. A coupling material is typically used in such applications to keep a constant distance between the transducer and the interior wall of the rectum. There are currently several methods for using coupling materials on probes; however, there are problems associated with each method.
One type of coupling material is a block of soft silicon that is placed over the transducer to create a spacer between the transducer and the surface being examined. The silicon spacer typically extends an eighth of an inch or more from the face of the transducer and thus increases the diameter of the probe by the same amount. Since the structure of the silicon spacer is generally firm, a constant distance is maintained between the transducer and the surface being examined, even as pressure is applied to the silicon spacer. The constant distance created by the silicon spacer permits the user to manipulate or maneuver the probe within the rectum without distorting the focus of the transducer. The user can also use the spacer to stabilize the prostate by applying pressure to the interior wall of the rectum.
A drawback to a silicon spacer is that it is attached to the probe before it is inserted into the body. The size of the silicon spacer adds to the size of the probe, and the patient being examined may incur discomfort or pain when the probe and silicon spacer are inserted into the body. Also, once the probe and spacer are inside the body, the distance between the transducer and the surface being examined cannot be modified by the user without removing the probe from the body and re-inserting the probe with a different size silicon spacer.
Prophylactic materials or condoms filled with water are currently used to eliminate the discomfort caused by silicon spacers. In such applications, a condom is placed over the probe and sealed at one end before it is inserted into the body. Once the condom covered probe is inserted into the body, water may be introduced into the probe through an external port on the probe. Since the condom is sealed at one end, the condom inflates when the water is introduced. The water filled condom creates an acoustic coupling between the transducer and the surface being scanned.
Since the outer surface of the condom is unrestricted, the condom expands over its entire surface area as more water is introduced into the condom. For example, in prostate procedures, the condom is typically inflated until the entire rectum is filled. When the condom is inflated in such a manner, the condom conforms to the interior walls of the rectum and becomes stationary while the probe moves freely within the condom. Not only does such a method cause discomfort to the patient, the free movement of the probe creates several problems.
As stated above, it is desirable to maintain a constant distance between the transducer and the surface being examined to keep the transducer focused. The water-filled condom provides no resistance against the probe and thus allows the probe to come into contact with, or in close proximity to, the condom itself. In such cases, the coupling effect of the water is eliminated. Moreover, a probe with an inflated condom around its circumference cannot be used to stabilize an organ while the organ is being scanned by the probe. To stabilize an organ such as a prostate, the probe must be pressed against the interior wall of the rectum. However, as soon as the probe is pressed against the interior wall of the rectum, the water coupling is eliminated due to the lack of resistance from the water.
Also, since the probe moves freely within the condom, it is difficult to maintain a constant distance between the transducer and the surface being examined. If the distance varies while the probe is scanning, then the probe becomes unfocused and the image quality of the scanned region may become diminished.
Accordingly, it is desirable to have a guide for controlling the size and shape of coupling material while also maintaining a constant distance between the transducer and the surface being examined. The guide should maintain the constant distance even if the probe is moved during the scanning procedure. It is also desirable to have a guide that will allow the coupling material and probe to be used to keep an organ stable while the organ is being scanned. It is also desirable to have a guide that minimizes discomfort to the patient.
In accordance with the principles of the present invention, a coupling guide is provided for controlling the size and shape of a condom covered probe when the condom is inflated with a fluid such as water. The inflated portion of the condom maintains a constant distance between the transducer and the surface being examined, even if the probe is moved during the scanning procedure. The present invention allows an inflated condom and probe to be used for stabilizing organs while the probe is scanning the organ. The present invention also minimizes discomfort to the patient.